Treatment of liquid systems and apparatus therefor



A. SZEGVARI Sept. 25, 1956 TREATMENT OF LIQUID SYSTEMS AND APPARATUSTHEREFOR Filed May 24. 1950 5 Sheets-Sheet l I N V EN TOR. ANDREW 5256V4)?/ Ffi ATTORNEY Sept. 25, 1956 szEGvAR: v 2,764,359

TREATMENT OF LIQUID SYSTEMS AND APPARATUS THEREFOR Filed May 24, 1950 3Sheets-Sheet 2 IN V EN TOR.

ANDREW 52 56 mm m WM A T TORNE Y A. SZEGVARI Sept. 25, 1956 TREATMENT OFLIQUID SYSTEMS AND APPARATUS THEREFOR Eiled May 24 1950 3 Sheets-Sheet 3INVEN TOR. ANDREW Sztamm United States Patent TREATMENT OF LIQUIDSYSTEMS AND APPARATUS THEREFQR Andrew Szegvari, Akron, Ohio ApplicationMay 24, 1950, erial No. 163,837

11 Claims. (Cl. 241-15) The containing attritive or grinding elements,and agitating I means adapted to be moved through these elements.

In particular the process is carried out by bringing about an activatedcondition of the attritive elements characterized by at least a partialrandom distribution of their momentum. It is not necessary thatthemovement be entirely random, and in the preferred operation moreparticularly described herein there is a superimposed drift of theelements in a circular and axial direction. The average momentum of theelements at the point of contact is large enough to overcome theresistance of the particles to subdivision.

' The invention includes the grinding of solids to reduce theirgeometrical or physical particle size, the mixing of two or moredifferent solids, and the suspension of one or more finely dividedsolids in a liquid.

The process and apparatus have particular value. in fine grinding,especially in the presence of a liquid. By fine grinding is meantgrinding to a particle size smaller than 50 microns, and approaching andextending into the colloidal range; for instance as far as to an averageparticle size of 2 microns, or 0.5 micron, or less.

An attritor is a vessel which contains a large number of attritiveelements which may be flint pebbles, balls of metal, etc. The attritionis produced by the movement of an agitator through the bulk of theattritive elements. The relation of the essential components of theapparatus and other processing details, in particular of the agitator tothe mass of attritive elements is such that the movement of the agitatormaintains a condition of relative unrest between the adjacent attritiveelements through- 4 out the greater part of the mass of elements. Theremay be little or no movement around the edges and the bottom of thevessel, but the number of elements which are not maintained in continualmotion is small. The movement of the elements is produced not only bycontact with the agitator but the kinetic energy imparted to theelements contacted by the agitator is transmitted by them to adjacentelements, maintaining substantially the entire mass of the attritiveelements in continual motion having a certain random distribution of themomentum of the contacted elements. Each of the activated elementsrepeatedly and continuously bounces from contact with one element intocontact with another element and with the agitator, and remains insuspension in the system; The most efiicient operation is that in whichthe number of contacts or collisions between adjacent attritive'elements leading to subdivision of the material being treatedapproaches, or reaches, the largest possible statistical probability.

The more rapid the movement of the agitator the larger the number ofcontacts. Furthermore, the'greater 'ice the amount of energy transmittedto the contacted elements, for subsequent transmission to adjacentelements, the larger the number of contacts. The grinding action towhich this invention relates is dependent upon the contactinginteraction between the attritive elements. The attrition between theelements and both the agitator shaft and the walls of the vessel ispreferably minimized to prolong their life.

The number of contacts is dependent upon various other factors. Forinstance, the number of contacts depends upon the type of agitation andthe nature of the movement of the-agitator. A very efiicient type ofagitator for use in an upright cylindrical vessel is one formed of acentral shaft and agitating arms. This is preferred for wet grinding.For dry grinding two such agitators may be used spaced farther apartthan the length of the longest agitator arm, so that the agitator armsoverlap.

It was found that under certain conditions the movement of the agitatorarms through the body of attritive elements kinetically activates themand maintains such a condition. Kinetically activated by the agitatingdevice, means to imp-art continuously sufficient mechanical energy to alarge enough number of the elements so that a random distribution of themomentums coupled with an incipient free path develops. This conditionis related to that underlying all natural phenomena based on behavior ofa multitude of elements having mechanical energy as in the case with gasmolecules in free space. The activated elements are kept out of staticcontact with one another and continually interact with one another, withresultant subdivision of the material which is being acted upon.

The creation of this activated condition of the attritive elements bythe activating device, such as the agitator, is very significant anddescribed in the following. It is very different from the action of thegrinding elements in a ball mill which is the equipment which is mostwidely used for fine grinding at the present time. In the first place,the grinding elements used in equipment of the type here described aremuch smaller than those generally employed in a ball mill. This isadvantageousbecause the smaller elements produce a larger number ofgrinding contacts or collisions than thesame volume of larger elements.In the second place, in a ball mill the grinding action is greater or asgreat at the inner surface of the mill as in any other place, whereas inthe preferred equipment of this invention the maximum activity isconcentrated away from the walls of the vessel and this prolongs thelife of the vessel. The agitator transfers mechanical energy to theattritive elements and maintains a condition of activated motion andrelative unrest between the adjacent elements throughout the greaterpart of the mass of the elements.

The activated condition of the elements and therefore the number ofeffective contacts between'the elements and their attritive action onthe material to be ground, is dependent on the depth of the bed of theattritive elements, the specific gravity of the liquid if any bepresent, the speed of the agitator, the size of the attritive elements,the distribution of the size of these elements, the shape of theseelements, and on the viscosity of the liquid.

The influence of the depth of the bed of the attritive elements is suchthat as the settling tendency is increased a larger momentum has to betransferred to the elements to keep them in an agitated state; thisrequires an increased speed of agitation. If the agitator must beo'perated at an optimum speed in any given vessel operating on a givenmaterial, the depth of the bed of attritive elements will have apractical optimum.

The specific gravity of the liquid counteracts the influence of depth;in other words, the higher the specific gravity of the liquid, thegreater the depth of the bed of attritive elements that can be kept inan activated condition with the same R. P. M. of the agitator.

The R. P. M. of the agitator has a direct influence on the amount ofmechanical energy which is transmitted to the attritive elements fromthe agitator arms. The higher the speed, the greater the energytransmitted, and the more effective the random distribution of momentumto the elements leading to attritive action. However, an increase in theR. P. M. of the agitator beyond a certain limit, increases the motion ofthe attritive elements without producing a corresponding increase intheir random action and causes their impinging on the side of the tankwith increased wearing action. The wearing of the tank depends on theclearance between the agitator arms and the side of the tank, thus thisclearance has a direct relation to the most practical agitator speed.

As to the size of the grinding elements, the smaller these elements, thelarger the fine grinding capacity of a given volume of the elements. Itwas found that the geometric probability factor of the number ofeffective contacts between the attritive elements and thus the finegrinding capacity of a given volume of attritive elements is inverselyproportional with the square of the diameter of the attritive elements.However, a decrease in the size of the elements decreases the randommomentum imparted by the agitator to the elements. This decreases the Iattritive action on the material to be ground. While this can becounter-balanced by an increase in the R. P. M. of the agitator, thecondition is such that there is an optimum size of the attritiveelements which depends on the other conditions mentioned.

As to the distribution of size of these attritive elements, it issignificant that they should be substantially uniform in. size withlittle deviation. One or a few larger elements mixed with smallerelements are not activated as much as the smaller elements, and preventoptimum performance. Likewise, they interfere with the free movement ofthe smaller elements and cause the whole bed to jam, leading todestructive action on the attritive components. Such larger elementsalso prevent maintenance of calculated clearance conditions between theends of the agitator arms and the inner wall of the vessel.

As to the shape of the attritive elements, it is preferred that theyhave the same dimensions in all directions. If they are much larger inone direction than in the other, they will greatly interfere with therandom distribution of the momentum imparted to the elements. Also, theywill cause jamming of the attritive elements much as larger elementsmixed with smaller elements cause it to jam. Non-uniformity in the sizeof the elements and the presence of elongated elements greatly reducethe maximum possible R. P. M. at which the agitator may be operated in agiven machine. This reduces the output of any given equipment due to thedecreased attritive action between the grinding elements far below whatcan be obtained under optimum conditions. It should be added here thatthe clearance between a rotating activating device and the walls of thevessel has a definite relationship to the controlling factors mentionedabove; in other words, to obtain the optimum conditions, the clearancemust be varied with changes in the speed of rotation. It should beincreased for higher grinding speeds.

Finally, it should be added that the size of the material to be groundhas an influence on the most efficient speed to be used in any set ofconditions. If the size of this material is initially large, a certainminimum momentum of the attritive elements is required to subdivide it.This is larger than the minimum required for a starting material ofsmaller particle size. The space-time concentration of binary contacts(collisions) between attritive elements operating on materials ofsmaller particle size can be increased over that required for eflicientaction on larger particles.

The attritive elements will ordinarily be no larger than inch indiameter. They will usually be larger than 7 inch in diameter, althoughsmaller elements may be used in low viscosity liquids and possibly inother operations. For an attritor of small size, for example one havinga capacity of one pint to one gallon, smaller grinding elements of A toA inch in diameter will ordinarily be employed, the size of the elementsdepending upon the size of the vessel. In commercial units having acapacity of 60, or gallons, elements i /2 or W inch in diameter willgenerally be used, the smaller units being employed with smaller vesselsand the larger ones with the larger vessels.

The most efiicient depth for a bed of elements will depend upon the sizeof the elements, the R. P. M. of the agitator, and the differencebetween the specific gravity of the elements and the liquid in whichthey are immersed. For instance, in the case of a grinding tank 30inches in diameter, using flint elements A inch in diameter, with theagitator operating at 65 R. P. M. in liquid with a specific gravity of1.0, the most efficient depth for the bed of elements is 22 inches.Using similar equipment with a liquid having a specific gravity of 1.6,a bed 26 inches deep is most eflicient.

The speed of rotation of an agitator is dependent on its diameter, i.e., th length of its arms, because the longer the arms, the faster theirends move, and the greater the agitation produced. Thus, in a laboratorystyle attritor with agitator arm's 1 1 inch long (i. e., 2 /8 inches indiameter), elements inch in diameter are recommended and 350-450 R. P.M. will give etficient operation. In a production attritor containingelements inch in diameter with arms 13 inches long (i. 'e., 26 inches indiameter), 65 R. P. M. has been used.

Suflicient clearance should be provided between the ends of the agitatorarms and the wall of the vessel. The amount of clearance required willvary with the speed of the agitator. At 60 R. P. M. a minimum distanceequal to three element diameters is recommended if the elements are inchin diameter; therefore a clearance of 1 inches is recommended at the endof each arm. If the speed is 80 R. P. M. using the same size of grindingelements a clearance of five element diameters or 2 5 inches isrecommended. Thus, in a vessel 36 inches in diameter, using elements Winches in diameter, operating at 60 R. P. M., agitator arms should beabout 16% inches long. Operating at 80 R. P. M. in this vessel agitatorarms of about 15%; inches will be recommended.

Although for most effic'ient operation, a vessel with a dished bottommight be recommended, from an engineering standpoint it is mostpractical to construct the vessel with a flat bottom. Usually acylindrical wall will be provided. The agitator will be mounted such adistance above the bottom that there is no movement, or substantially nomovement of the elements at the bottom of the bed. The bottom arm ispreferably somewhat shorter than those above it. Those 'arms above thebottom arm will advantageously be arranged in pairs and spacedsufficiently to permit the liquid to pass between them. Such arrangementof the arms in pairs provides efiicient agitation with minimumhydrodynamic resistance. The resistance is much lower than that of anarm with a diameter equal to the combined diameter of the pair plus thespace in between them. Such a large arm would also be expensive andheavy. Of the two arms in each pair, one is preferably located at aslight angle to the other so that "as the agitaator is rotated the armsproduce a lifting tendency at the periphery of the tank which decreasesto zero as the central shaft of the agitator is approached. Thus, theaction of this agitator assists the natural tendency for the liquid in arotating Cylindrical system to circulate outwards at the bottom, upwardsat the sides, inwards at the top, and downwards at the center.

The maximum activity is concentrated away from the wall of the vessel tominimize wear. The elements adjacent the wall are subjected to minimummovement. The activity is greatest around the ends of the arms anddecreases as the center of rotation is approached. To prevent excessivewear it is desirable to coat the arms with a very hard alloy, such as atungsten alloy, etc.

The invention will be further described in connection with the drawingswhich show more particularly an attritor designed for use in production.It may have a capacity of, for example, 50 gallons to 100 or 150gallons. An attritor for laboratory use may have as small a capacity asa pint and may have a capcity of a gallon or two. The smallerrattritors, whether for laboratory use or for production, may beconstructed on a base plate which is designed to slide on rails. in therails through which there is a rod which is fastened to each edge of thebase plate it is possible not only to slide th vessel in and out fromunder agitator driving means, but by thus mounting the vessel it may betilted readily when desired. The lateral relation of the vessel and baseplate to the rails should be maintained constant so that when the vesselis slid under the agitation driving means the drive shaft and theagitator shaft are in lateral alignment.

Whether in a laboratory size attritor or a larger one for productionuse, the drive shaft is advantageously operated from a worm gear. Thisprevents manual rotation of the drive shaft. Manual rotation of theagitator shaft is also prevented by the resistance afforded by thepresence of the attritive elements around the agitator blades.Therefore, the coupling means must be such as to permit union of theagitator shaft to the drive shaft regardless of the angular relation ofthe one to the other, or the angle of rotation at which the agitator islocated in the vessel. For production equipment such coupling means musthold the agitator shaft to the drive shaft firmly enough to preventslippage in spite of the fact that the rotation of the agitator mustovercome the resistance afforded by the presence of the attritiveelements.

In the drawings Fig. 1 is a front elevation, partly broken away, of theattritor;

Fig. 2 is a section on the line 2-2 of Fig. 1;

Fig. 3 is an enlarged detail of the clamping means taken on the line 3-3of Fig. 1;

Fig. 4 is a detail showing the operation of the clamping means;

' Fig. 5 is a side view of the attritor with the vessel turned throughan angle of 90;

Fig. 6 is a detail on the line 66 of Fig. 5 showing means for lockingthe attritor in an upright position;

Fig. 7 is a detail on the line 77 of Fig. 5 showing the screen clampingmeans;

Fig. 8 is an enlarged section of the outlet valve from the attritor;

Fig. 9 is a section on the line 99 of Fig. 8;

Figs. 10a, 10b, and 100 are elevations on the line 1010 of Fig. 8showing the valve in open, partly open, and closed position,respectively; and

Fig. 11 is an exploded view showing the three essential parts of thevalve, each partly broken away.

The drawing illustrates an 'attritor of the type which may be used toadvantage in production, particularly for the dispersion of finelyground solid particles in a liquid. The vessel 1 provided with thejacket 2 is supported at each side on trunnions 3 and 4, which in turnare supported in hearings in the triangular side plates Sand 6respectively. These side plates are in turn supported on grooved wheels10 which are adapted to be rolled back andforth on :the'track 11. Thusthe vessel 1 is mounted- By providing slots to be rolled back and forthon the track to bring the agitator under the drive means or to bring thevessel forward for dumping. A flexible conduit is fastened to theopening 13 to supply cold (or, if required, hot) water or other liquidto the cooling jacket 2 to provide tern.- perature control. The jacketmay be drained through the valve-equipped hose 14 into the receivershown, or to other suitable discharge means.

The agitator is formed of the central shaft 15 and the arms 16, 17, 18,19 and MP. It is supported only by the coupling which holds it to thedrive shaft 22. The motor 23 drives a worm gear (not shown) in thehousing 24, which in turn rotates the shaft 22 in the diredtionindicated by the arrow in Fig. 2. The shaft 15 is clamped to it anddriven by it. I

The four upper arms 17, 13, 19 and 20 are arranged in pairs. The lowerarm of each pair is slightly forward of the upper arm so that when theagitator is rotated in the direction indicated by the arrow the armstend to facilitate movement of any liquid in the attri tor upward aroundthe outer surface of the vessel, then inward across the top of thevessel, downward around the shaft 15, and outward at the bottom. Thespace between the arms of each pair is not more than three elementdiameters. (For instance, using attritive elements /2 inch in diameterit will not be more than 1 /2 inches.) However, the space between thearms of each pair is such as to permit the flow of liquid between themtogether with any matter suspended in the liquid.

To facilitate circulation of the liquid in the vessel the attri to-r isequipped with a pump 39 driven by the motor 31. This draws off liquidfrom the top of the vessel through the intake pipe 32 and discharges itthrough the flexible conduit 33, back through the valve 34 into thevessel. During any grinding operation all of the liquiddrawn off throughthe intake pipe 32 is returned to the vessel through the conduit 33.Opposite the inlet 36 of the valve to which the conduit 33 is connectedis a discharge opening 37 to which is connected a hose or other type ofconduit (not shown). This latter conduit is provided with a valve andwhen the operation of attrition is completed, on opening this valvethecontents of the attritorare discharged into any suitable receptacle.Alternatively, the vessel may be discharged by being dumped, asillustrated in Fig. 5. Likewise, the'vessel may be discharged throughthe valve 34 by reversing the pump 30 and either pumping the liquidthrough the conduit 32 which may be of flexible construction, orproviding a T in the conduit 32 and suitable valves to convey the liquidfrom the pump away from the vessel.

The motor 23, housing 24, rails 11, pump 39 and motor 31 are allsupported by the sturdy frame 40. If the vessel is to be dumped insteadof being discharged through the valve 34, the screen 41 is fastened overthe top of the vessel by the dogs 42 (of which only one is shown). Thescreen may be in two halves and fit snugly The lock which holds thevessel" around the shaft 15. upright is then unlocked. The handle 44.(Fig. 1) is fastened to the rod 45 which is fastened to the link 46 atthe rear of the attri tor. clockwise condition lowers the outer end ofthis link 46, lifting the opposite end of the adjacent link 47, liftingbolt 48 out of its hole in plate 49. When the bolt 48 is lifted thevessel can be moved forward on the track 11. The crank handle 50 isturned, and this in turn rotates the worm 51 which is meshed with thegear 52 which is fastened to the side of the vessel. By rotating thehandle 50 the vessel is dumped. The spout 53 directs the materialdischarged from the vessel.

After the vessel is emptied it is returned to the upright position androlled back on the track until the agitator Thev shaft 15 is directlyunder the driven shaft 22. coupling of these shafts must be such as tofasten them securely together regardless of the relative angularposition of the two shafts.- It is impossible to manually Turning thehandle 44 in the- 7 rotate the agitator because of the presence of theattritive elements which cover the arms in the vessel. It is furtherimpossible to manually turn the shaft 22 because it is driven by theworm gear. It is, therefore, necessary to clamp the two shafts togetherwithout adjusting them to any predetermined angular relationship.

The operation of the clamp is illustrated in Fig. 4 and the details ofone clamping element are illustrated in Fig. 3. The disc fitting 55 isfastened to the shaft and the disc fitting 56 is fastened to the shaft22. Both discs are circular and the upper disc 56 is countersunk toreceive the disc 55. The fittings are keyed to the respective shafts bythe keys 58 and 59. Set screws 60 prevent vertical movement of thefittings on the shafts.

Three clamps are pivotally fastened to bosses 62 on the upper fitting.An angular member 63 is pivoted to each boss by the pivot 64. The handle65 which is swivelly attached to member 63 provides a convenientleverage for the operation of the toggle coupling.

The lower member 70 of the clamp is pivoted at 71 to the angular member63. The lug 73 on the lower member projects inwardly and the set screw74 is screwed through it. To clamp the two shafts together the threehandles 65 are swung upwardly bringing the set screws 74 to bear againstthe lower surface of the disc 55. The screws are tightened in thisposition. The tighter the screws are drawn the more the pivot 71 isdrawn inwardly and downwardly. At the interface of the discs is thefabric liner 77. This may be treated with oil or asphalt or the like togive it wearing qualities. It is preferably cemented to the upper discbut may be cemented to either disc. One such liner may be fastened toeach disc. This cushions the clamps and prevents slippage.

The valve 34 is especially designed to operate successfully inconcentrated liquid slurries which because of settling, will rapidlyclog a conventional valve. It satisfies the following requirements:

A. There is no dead space between the inside of the tank and the closingmember of the valve, so that if the valve is closed no settling of theslurry can take place.

B. The closure itself is constructed so that the operation of the valveinvolves automatic cleaning of the openings through which the liquidflows when the valve is open.

C. The valve body 80 itself is swept free from settled material by abuilt-in sweeping device which operates when the valve is operated.

The housing 80 is cylindrical. The end plate 81 is fastened onto it bythe bolts 82. Gasket material 84 is held to the outer surface of thehousing by the clamping ring 85. The outer end of it is located betweenthe cover plate 86 and bosses 87 in the wall 88 of the jacket. The plate86 is fastened into the bosses by the bolts 89. The inner end of thevalve slides into the opening in the wall of the vessel 91 bounded bythe ring 92. This ring is welded to the wall 91. O-rings 95, 96 and 97,located between the wall 80 and the ring 92, and also at the outer endof the valve, prevent leakage.

The'inner end of the valve housing is closed by the stationary plate100. This is covered by the screen 101 which is likewise stationary. Inclose contact with the plate 100 is the rotatable valve head 102. Pins104 in the end plate 100 fit into the circular grooves 105 in the valveplate 102. Pins 107 on the inner surface of the valve plate 102 fit intothe grooves 108 in the end plate 100. The valve plate 102 is connectedby the stem 110 with the valve handle 111. The webs 115 fastened to thestem 110 support the scrapers 116. As thevalve handle 111 is turned thescrapers 116 prevent the accumulation of solid matter on the wall of thehousing 80. Likewise, as the valve handle 111 is turned the valve plate102 is rotated against the surface of the end plate 100. As the valveplate 102 is rotated the pins 104 and 107 clear away any deposit ofsolid matter which may form in the slots 105 and 108 respectively. Thescreen 101-prevents any 8 of the attritive elements 120 (Fig. 8) fromlodging against the slots 108. The length of the diameter of theopenings in the screen is the same as the width of the valve slots 108.Thus the slots are small enough to prevent the attritive elements 120from entering them. The purpose of the round orifices of the screen isto prevent elongated elements (such as might be formed by fracture orwear of the spherical attritive elements) from lodging in the openings108. The screen 101 is necessarily thin so that any settling within thecavity represented by such orifice cannot take place. There is thus nopossibility of these cavities becoming plugged. The plate is thick andstrong enough to withstand any pressure developed within the vessel 1and the mechanical action of the attritive elements. that suspendedmatter can settle in them and plug the slots. The pins 107 remove anysuch potential deposit when the valve is turned. Thus the valve is usedin a system in which there is suspended matter of two different sizes,permits the passage of the fraction of the smaller sizes while excludingthe fraction of the larger sizes, and it stays operative in spite of thetendency for deposit formation.

The pins 104 and 107 are in line with the slots 108 and 105,respectively, and are spaced a short distance from the end thereof. Whenthe valve is closed the two plates overlap to this extent. Fig. 100shows the valve closed with the pins 104 moved to the end of the slots105, and in dotted lines it shows the pins 107 at the ends of the slots108. When fully opened (Fig. 10a) the pins 104 (which are stationary)are located in the opposite ends of the slots 105. The pins 107 on thevalve plate 102 are turned through an angle somewhat less than 180 andare in the ends of the slots 108. Over the greater part of theirrespective lengths the slots coincide and provide an opening through thevalve. Liquid and suspended solid matter are circulated through theseopenings by the pump 30 and connecting conduits. Fig. 10b shows thevalve only partially opened. The curved slots and 108 coincide over onlya portion of the distance-between the pins 104 and 107. Thus, this valvepermits free flow of the liquid and suspended matter and preventsaccumulation of such matter when the circulation of liquid ceases or istemporarily slowed down.

The flexible conduit 33 connects with the chamber which is open at bothends and provided with the connections 36 and 37 (Fig. 2). By pluggingthe opening 37 or closing a valve in the draw-01f conduit attached tothis connection the liquid circulated by the pump 30 is returned throughthe valve head 102 into the bottom of the vessel. If the contents of thevessel are simply to be drained through the valve the opening in theconduit attached to the connection 37 will be open and the valve head102 will be turned to the opened position so that the liquid can drainout through the valve.

The attritor can be used for a multitude of different operations. Thus,it may be used for grinding pigments which are not to be used insuspension in liquid but which, after grinding, are separated from theliquid used in the attritor. The separation may be accomplished in anyusual manner. The following examples illustrate applications of theattritor:

Example I Ultramarine blue pigment which as originally processd containsparticles up to 60 microns. It has to be subdivided to consist ofessentially 4 microns or smaller particles. This is carried out in theform of a water slurry; and using conventional pebble mills requires 24to 48 hours. The same or better effect can be obtained in an attritor in2 to 4 hours. For example, a l30-gallon attritor may be used, the tankof which is 35 /2 inches in diameter and 40 inches high. This isequipped with an agitator of the type illustrated in the drawings inwhich the four upper arms each measure 29% inches from tip to tip,giving a clearance of 3 inches at the end of each shaft. The tankcontains 900 pounds of specially processed The slots 108 are thereforenecessarily so deep a? rounded flint 7 inch in diameter. This is suitedfor rotation of the agitator at 80 R. P. M. For more rapid rotationsmaller flint elements will be used and the time required will bereduced.

A 50 per cent slurry of the ultramarine is made in water containing 1per cent of ammonia and 0.5 to 2 per cent or" a dispersing agent, suchas naphthalene sulfonic acid derivative. 75 gallons of such slurry isfinely ground in this attritor and reduced to the desired particle size.

The finely ground ultramarine may be separated from the liquid in anyusual manner.

Example I] The attritor is used advantageously to produce andsimultaneously suspend finely divided particles in a liquid. Thus, forexample, in the preparation of dispersions of compounding ingredients tobe used in latex for the production of foamed rubber products or dippedgoods, etc., the dispersions of compounding ingredients may be moreadvantageously and more cheaply prepared in the form of dispersions inan attritor than in conventional equipment. The following illustratesthe preparation of compounding ingredients to be added to a rubberlatex.

One hundred parts of sulfur, 50 parts of phenyl naphthylamine, 50 partsof a mercaptobenzothiazole derivative and 250 parts of zinc oxide areslurried into a water solution containing 0.5 per cent ammonia and l percent of a dispersing agent such as either Darvan made by the Dewey &Almy Chemical Corporation, or Marasperse made by the Marathon PaperCompany. Forty gallons of such slurry are ground in an attritor tankhaving a 75-gallon capacity and containing 600 pounds of /2 inch flintpebbles. This tank measures 28%; inches in diameter and is provided withan agitator of the type illustrated in the drawings, the four upper armsmeasuring 22% inches from tip to tip. Operating at 75 R. P. M. thecomposition is reduced to an average particle size of less than 0.5micron in five or six hours grinding. It would take 90 hours to producethe same eifect in a conventional pebble mill.

Example III In the following example, the finely ground product will beused as a slurry without separation from the liquid medium.

It requires 24 to 48 hours in a conventional pebble mill to reduce atitanium dioxide alkyd paste containing 50 per cent titanium dioxide toa particle size of 7.5 to 8 North Gauge reading. When 400 grams of sucha crude paste is placed in a laboratory size attritor using its inchstainless steel balls, an agitator with arms measuring2 /2 inches fromtip to tip with inch clearance between the end of each arm and the wallof the vessel, and rotating the agitator at 400 R. P. M., the paste willbe reduced to the above fineness in 20 to 30 minutes.

Such an operation may be carried on efiiciently in a larger attritor,such as those referred to in Examples I and II. In a laboratory attritorthe arms are not usually arranged as shown in the drawings but may beplaced individually, and at right angles to one another. A wide choicein the arrangement of the arms is possible.

Thus it is seen that the action of the attritor and the factorsinfluencing the effect of the attritive action of the elements is quitedifierent from the action of the grinding elements in a conventionalball mill and the effect of their action. The attritor offers variousadvantages over the ball mill, both from the standpoint of constructionand convenience of operation and from the standpoint of efficiency.Thus, on one hand an attritor may be made several times as efficient, e.g., 20 times or more, as the most eflicient ball mill, thereby reducingthe time required to complete a certain action. On the other hand, theconvenience of its operation is of greatest practical significance.

A ball mill is mounted horizontally and is charged and dischargedthrough an opening in its cylindrical wall.

iii This opening must be brought to the top of the mill when the mill isto be charged and it is brought to the bottom of the mill to dischargethe mill. While operating the cover must be tightly sealed on the mill.A particualr advantage in the construction of the attritor is that theattritor need not be covered and there is no danger of building upexplosive pressure inside of an attritor as there is Within a ball mill.Whether the attritor is covered during an operation or not, it isrelatively easy to charge it. Further, it may conveniently be providedwith means for dumping the entire charge when an operation has beencompleted. Furthermore, in various operations it is desirable to addsome reagent a little at a time. To conduct such an operation in a ballmill it is necessary to stop the mill and open it and then close itagain for each addition. In the operation of an attritor, particularlyif the top of the attritor is open, the addition may be made evenwithout stopping the agitator. A further advantage over ball milloperations is that the attritor may be conveniently jacketed for coolingand heating, whereas the jacketing of a ball mill is impractical, or atbest exceedingly expensive.

What I claim is: I

l. The method of treating a heterogeneous liquid system in an enclosurein which are a large number of relatively spherical attritive elements,which method comprises continuously moving an agitator through theelements thereby displacing the elements in its path, all of theelements being substantially the same size, and the speed of movement ofthe agitator being sufficient to impart to at least most of the elementsa movement having at least a partially random distribution causing eachof said elements to repeatedly and continuously bounce from contact withone element into contact with another element and with the agitator, andremain suspended in the system.

2. The method of treating a heterogeneous liquid system in an enclosurein which are a large number of relatively spherical attritive elements,all of substantially the same size, which method comprises rotating anagitator through the elements at a speed between substantially 450 and60 revolutions per minute thereby displacing the elements in its pathand imparting to at least most of said elements a movement having atleast a partially random distribution causing each of said elements torepeatedly and continuously bounce from contact with one element intocontact with another element and with the agitator, and remain suspendedin the system.

3. The method of treating a heterogeneous liquid system in an enclosurein which are a large number of relatively spherical attritive elementswith a diametric measurement between substantially and W inch, but allof substantially the same size, which method comprises rotating anagitator through the elements at a speed between 450 and 60 revolutionsper minute thereby displacing the elements in its path and imparting toat least most of said elements a movement having at least a partiallyrandom distribution causing each of said elements to repeatedly andcontinuously bounce from contact with one element into contact withanother element and with the agitator, and remain suspended in thesystem.

4. The method of treating a heterogeneous liquid system in a vessel inwhich is a rotatable agitator immersed in the liquid and at leastpartially covered with relatively spherical attritive elements with adiametric measurement between substantially 7 and W inches in diameter,but all of substantially the same size, which method comprises movingthe agitator through the attritive elements at a speed in the range ofsubstantially 60 to revolutions per minute, thereby displacing theelements in its path and imparting to at least those elements locatedaway from the bottom and cylindrical wall of the vessel a movementhaving at least a partially random distribution causing each of saidelements to repeatedly and 11 continuously bounce from contact with oneelement into contact with another element and the agitator, and remainsuspended in the system.

5. The method of treating a heterogeneous liquid system in an uprightcylindrical vessel provided with a'central agitator having substantiallyhorizontal agitating arms, the vessel being filled with attritiveelements to a height such that at least the bottom arm of the agitatoris covered by them, the elements being relatively spherical with adiametric measurement of substantially 73 to inches, but all ofsubstantially the same size, with the end of each arm at least threetimes the diametric measurement of the elements away from thecylindrical wall, which method comprises rotating the agitator at aspeed of substantially 60 to about 450 revolutions per minute dependingupon the size of the elements, the smaller the elements, the higher thespeed of rotation of the agitator, and by such rotation imparting atleast a partially random distribution to the elements located away fromthe wall causing each of them to bounce from contact with one elementinto contact with another element and with the agitator, and remainsuspended in the system.

6. The method of treating a heterogeneous liquid system in a vesselequipped with an agitator and containing a large number of relativelyspherical attritive elements, all of substantially the same size, whichcover at least the bottom of the vessel and embed at least the lowerportion of the agitator, which method comprises moving the agitator anddisplacing the elements in its path, the speed of movement of theagitator being suflicient to impart to all of the attritive elementswhich are located away from the bottom and the side of the vessel atleast apartially random distribution causing each of said elements torepeatedly and continuously bounce from contact with one element intocontact with another element and the agitator, and remain suspended inthe system; while providing a relatively motionless layer of theelements over the bottom of the vessel, and a relatively motionlesslayer of the elements adjacent the side to a depth substantially equalin height to the height of said activated elements.

7. The method of treating a heterogeneous liquid system in a stationaryvessel, containing substantially spherical attritive elements all ofsubstantially the same size which comprises imparting to at least mostof the elements at least a partially random distribution causing each ofsaid elements to repeatedly and continuously bounce from contact withone element into contact with another element and the agitator, andremain suspended in the system, while adding to and subtracting from thesystem within the vessel and retaining the attritive elements in thevessel.

8. An upright substantially cylindrical vessel, an agitator shaftlocated axially of the vessel with means for rotating the shaft, armsextending substantially horizontally from the shaft, at least some ofthe arms being paired and separated from any other arms longitudinallyof the shaft.

by a substantially greater distance than the distance between the armsof the pair, the upper arm of each pair being angularly behind the lowerarm in the sense of the.

rotation of the shaft, and relatively spherical elements with adiametric measurement between substantially and inches, the elements allbeing of substantially the same size, the elements filling the vessel tosuch a ered with the attritive elements.

9. An upright, substantially cylindrical vessel with a vertical agitatorconcentric therewith the outermost part of which approaches the wall ofthe vessel, and contained in the vessel relatively spherical attritiveelements, all of substantially the same size, which elements fill thevessel to a height above the lower part of the agitator, there being aclearance between the outermost portion of the agitator and the wallnearest thereto which clearance is equal to at least three times thediameter of the elements.

10. A movable vessel equipped with an agitator on a substantiallyvertical shaft, and containing substantially spherical attritiveelements of substantially the same size which fill the vessel to aheight above the lower part of the agitator, drive means for the shaftlocated above the agitator, means at the top of the agitator shafthaving a horizontal top surface, the bottom surface of the drive meansbeing horizontal and in the same plane as the aforesaid surface, andtoggle clamps for clamping said surfaces together when the drive meansand shaft are concentric and said horizontal surfaces are in contact.

11. The method of mixing and grinding two solid components in a liquidsystem, in which there are a large number of relatively sphericalattritive elements of substantially the same size, which methodcomprises moving an agitator through the system at a speed sufficientlyto impart to at least most of the elements a movement having at least apartially random distribution causing each to repeatedly andcontinuously bounce from contact with one element into contact withanother element and with the agitator and remain suspended in thesystem, and thereby causing the two solid materials to be subdivided andintimately admixed with one another.

References Cited in the file of this patent UNITED STATES PATENTS441,419 Jones Nov. 25, 1890 919,112 Zinke Apr. 20, 1909 1,169,668Merritt Jan. 25, 1916 1,192,689 Sayer July 25, 1916 1,363,620 SellmanDec. 28, 1920 1,414,120 Fulcher Apr. 25, 1922 1,479,242 Johnson Jan. 1,1924 1,521,891 Kleinfeldt Jan. 6, 1925 1,605,025 Hildebrandt Nov. 2,1926- 1,652,929 Cawood Dec. 13, 1927 1,956,293 Klein et al. Apr. 24,1934 2,019,454 Larsen Oct. 29, 1935 2,208,892 Bukacek July 23, 19402,212,641 I-Iucks H Aug. 27, 1940 2,218,580 Kennedy Oct. 22, 19402,241,848 Eckart May 13, 1941 2,292,275 Kiesskalt Aug. 4, 1942 2,297,009Mead Sept. 29, 1942 2,577,353 Naidu et al. Dec. 4, 1951 FOREIGN PATENTS36,858 Germany Sept. 15, 1886 160,506 Switzerland June 1, 1933 OTHERREFERENCES Hard Surfacing by Fusion Welding, by Howard S. Avery, pub. byThe American Brake Shoe Co., New York. 1947. (Copy in Division 55.)

